Measuring instrument.



M. PICARD.

MEASURING INSTRUMENT. APPLIOATICN FILED 001'. 29,1908.

93 1 ,475 Patented Aug. 17, 1909.

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INYENTQR. MAURICE P\ CARD.

PATENT OFFICE.

'MAURICE PIGARD, OF PARIS, FRANCE.

MEASURING INSTRUMENT.

Specification of Letters Patent.

Patented Aug. 17, 1909.

1 Application filed October 2a, 1908. Serial No. 460,106.

To all whom it may concern:

Be it known that I, MAURICE PrcARD,a citizen of France, and resident of Paris, in the Department of the. Seine, France, have invented a certain new and useful Measuring Instrument, of which the following is a specification.

This invention relates to a measuring instrument of great precision comprising three stopsone of which may be moved by any suitable device relative tothe other two, one

of these latter being fixed while the other,-

which may be'moved in a direction parallel to the first, is solid with a piston movable in a cylinder containing a liquid and communicating with a tube whose mternal diameter is considerably smaller than the diameter of the said piston, in such a manner that a very slight movement of the iston or of its solid stop, causes a considera ble displacement of the liquid in the said tube.

The annexed drawing shows one embodiment ofthe invention 1n vertical section in Figure 1. Fig. 2 is a part plan of the instrument. certain sition.

As shown, the instrument comprises a members are shown in a different po- 30' rigid frame (1 having a slide-way b formed by the cleats b b in which may be moved, under the action located opposite two other sto s: one stop f is fixed to the frame while the otliier y can move, in a direction ,arallel to the sto c, with a sliding block 5 mounted in a s 'de-way 11, formed by the cleats t 1', and connected, by means of a rod is, with a piston 1 (Fig. 1) housed in a cylinder m communicating with a glass tube a, arranged vertically in the form of a barometric column whose internal diamwith each' other.

eter bears a fixed ratio to that of the cylinder m, this cylinder and the tube a being filled up to the zero point 0, with liquid, the piston being then at the outer limit of its movement, and the edges of the stops f and 9 being flush Under these conditions longitudinal displacement of 1 mm. of the piston Z in the cylinder causes the liquid in the tube a to rise to 100 mm. above zero.

The tube a has, at its upper end, a bent part 1) forming a chamber g containing a piece of cotton r impregnated with a substance for absorbin moisture, so that air entcring the tube w' be as dry as possible. This condition is particularly necessary in Fig. 3 is alike view to Fig. 2 in which of a micrometric screWc, a sliding block (1 carrymg a measurlng stop a,

the case where the li uid filling the cylinder m is mercury. A sea e 1 is disposed behind the tube 'n as shown.

A screw 8, screwed into the wall it of the cylinder permits, by penetrating'more or less into the cylinder, of regulating .the level of the liquid in the tube m so that this level will always be at the zero'point of the tube before making a measurement.

On the edge of the slideway b is a milli metric scale it and an index pointer 12 is fixed on the sliding block carrying the stop 6, so that this index is at the zero point of said scale when the stop e is in contact with the fixed stop f.

A spring a tends to'maintain constantly the stop g in exactly the same relative position as the stop f, that is to say, whenno measurement is made, or when the article to be measured is placed between the stops 6 and f, the face 1 of the sto g is exactly in alinement with the face 2 of the stop f. In this position the level of the liquid in the tube n will be exactly at zero.

The screw 0, which has a pitch of one milli meter,isoperated by a head 5 having a score 3 which must register exactly with a fixed index 4 when the two stops f, g are in contact with e and when the index '0 is at zero on the scale it.

To prevent the micrometric screw 0 fromon the drawing: this device may be one of the known types generally used in micrometers and callpers.

The 0 eratlon of the instrument is as follows piece 6 (Figs. 2 and 3) is to be measured: by means of the milled head 5 and screw 0 the stop e is moved away from the stop f until the piece '6 asses freely between the two stops then tiie stop e is rought nearer f by means of the milled head 5 until this turns without moving the screw 0: it can then be seen on the scale u that the index '0 has passed 5 mm. and that the score 3 on the disk 2 does not register with the index 4. The piece 6 is then placed between the stops e and g and the screw 0 is turned until the index 0 points to 5 mm. on the scale a and the score 3 of the button 2 registers with the index 4 (Fig. 3): the stop 9 will have been retracted for the difference between 5 mm. and the fraction of a millimeter by which the piece 6 issupposed uppose for example,'the width of a' to exceed 5 mm. This backward movement will have caused the liquid to rise in the tube 'n, from 0 to 7 (Fig. 1) and 73/100 is read on the scale 11. The mm. in thickness.

It will be understood that with a longer tube a and a ratio between the internal diameter of this tube and the diameter of the piece 6 is therefore 5.73

piston Z larger than in the exam le which as been described, it will be possi le to obtain a greater precision reaching up to 1/1000 or even to 1 10000 of a millimeter.

The form and the dimensions of'the different members of this instrument may vary.

The tube the level of the liquid in which indicates the fractions of the unit of measure on which the scale it is based need not necessarily be vertical.

Having now described my invention, I claim asnew and Wish to secure by Letters Patent:

In a micrometer, a movable stopactuated disp ment of the movable stop connected to the by a micrometer screw, and carrying apointer moving -on a scale attached to the slide-Way of the movable stop, in combination with apair of measuring sto s, one fixed, the other movable, the movab e member being-intepiston, substantially as set forth. v

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

MAURICE PIOARD.

Witnesses:

IIANsoN C. Coxn, JonN BAKER. 

